Electrical condenser



April 25, 1950 R. P. GUTTERMAN Erm.,

ELECTRICAL CONDENSER 2 Sheets-Sheet l Filed Nov. 1, 1948 miti,...

7 2 n M n t a 5, m m .z m 0 m 3 r k :w e k 2 m n e ,r M y .Tf M s B 2 G.P J .L 1/ x A e R E n R m M E u m m w m R m R. www, m QM. MN. .I hev\.\\\\\\\\.\`\\\\\\\\\\\\\\,\\\\\\`\`\\\,\\\N v 9 1 2 m m6 N o ...|n. dK p e A m Patented Apr. 25, 1950 ELECTRICAL CoNDENsER Robert P.Gutterman, Arlington, Va., and Alex J. Blelski, Minneapolis, Minn.,-assignors to Engineerlng Research Associates, Inc., St. Paul, Minn., acorporation oi' Minnesota.

Application November 1, 1948, Serial No. 57,778 15 Claims. (Cl.175-41.5)

This invention relates to electricalcondensers. More particularly, it isconcernedk with new forms of variable electrical condensers for use inradio, television or similar velectrical circuits.

A principal object of this invention is the provision of a new varietyof variable electrical condensers.

Further objects are as follows:

(l) To provide a spring-loaded structure in an electrical condensermaking possible highly accurate and reproduceable miniature condenserswhose mechanical components need not be held to exceedingly closetolerances.

(2) To provide a miniature variable condenser which is electricallyequivalent or superior to good quality variable condensers of standardtypes, but whose entire capacitive, actuating and indicating mechanismoccupies a very much smaller space.

(3) To provide a miniature variable condenser of the nature describedabove, comprising several coacting variable capacitive elements adaptedto track closely, electrically and mechanically, over the entireadjustment range.

(4) To provide an essentially totally shielded miniature variablecondenser.

(5) To provide a miniature variable condenser of one or more coactingcapacitive elements which may be conveniently adjusted and readjustedover its operating range with a relatively very high degree of accuracy.

(6) To provide a, variable condenser having control means and settingindicator means incorporated within a unitary casing.

(7) To provide a singleor multi-section miniature variable condenserwhose settings are essentially unaffected by shock and vibration.

(8) T0. provide a singleor multiple-element Avariable condenser whoseelements may be mechanically locked and unlocked at any point in theiradjustment range without affecting their setting.

(9) To provide a singleor multiple-section variable condenser in whichthe capacitive elements consist of mating sleeves of metal coated with asolid dielectric.

(10) To provide new forms of single-or multiple-section variablecondensers employing nickel oxide as the dielectric material.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription, while indicating preferred embodiments of the invention, isgiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

These objects are accomplished in accordance with the present inventionby forming variable condensers from pairs of telscoping metal tubes,having dielectric coatings interposed between engaging surfaces of themetal tubes, with the inner tubes of the pairs being carried axiallywithin a surrounding casing with a spring-loaded a1'- rangement andproviding the outer movable tubes with means for telescoping the tubesover the fixed inner tubes.

A more complete understanding of the structures involved with thisinvention may be had by reference to the accompanying drawing in which,

Figure 1 is a longitudinal sectional view of a variable condenserincorporating the features of this invention;

Figures 2 to 6 are transverse sectional views of the condenser of Figure1, taken along the lines 2-2 to 6 6, respectively, of Figure l.

Figure 7 is a partial longitudinal sectional view of the condenser takenalong the line 1 7 of Figure 4.

Figure 8 is a perspective view of the condenser.

Referring in detail to the drawings, the variable condenser 2 comprisesa plurality of stationary metal sleeves 4 and 5 and movable sleeves 6and 1, carried within a tubular casing or housing 8.

At least the outer surfaces I0 of the stationary sleeves or tubes 4 and5 and at least the inner surfaces I2 of the movable sleeves 6 and 1 areprovided with dielectric coatings. Preferably, the sleeves 4 and 6 aremade from nickel and are so treated as to have formed over the entiresurface thereof an adherent nickel oxide of sufficient thickness so asto serve as the dielectric coating, e. g., as prepared in accordancewith the disclosure of my copending applicationSerial Number 49,022,

filed September 13, 1948. Such oxide coats, when properly formed,electrically insulate the one tube from the other and are of highabrasion resistance so that the coatings on the tubes may slidablyengage during operation of the condenser without damage to theelectrical properties of the unit. This permits the inner tube to serveas a bearing element for the outer, movable tube. The outside diametersof sleeves 4 and 5 and the inside diameters of sleeves 6 and 1 should beheld to close tolerances so that clearance between the stationary andmoving sleeves is made just great enough to allow free motion of themoving sleeves.

Sleeves l and 5 are electrically insulated from each other andcorrespond to the separate stator sections of a standard two-sectionvariable condenser. Sleeves 8.and 1 are connected together electricallythrough metal sleeve or oscillatory member I3 and correspond to thedouble rotor elements of a standard two-section variable. condenser.

The tubular casing and sleeves are preferably of cylindrical shape,although they may be formed in other suitable configurations and thecasing is preferably made of metal, so as to serve as a shield for thecondenser, although it may be made of non-conducting material, such assyn..

thetic plastics or the like.

The stationary tubes 4 and 5 are carried axially within the casing 8upon a rod or shaft I4 which is fixed axially within the casing by beingfas-` tened at the end I8 to a bushing I8 which is pressed intothe end20 of the casing. A rivet 22 extends through the casing, bushing and rodholding the three elements in fixed relative position. The inner end 24of the rod I4 is of enlarged diameter having a circumferencecorresponding to about the outside diameter of the metal tubes 4 and 5with the radial shoulder 28 between thel enlarged portion 24 of the rodand the reduced portion 28 of the rod serving as a stop for the tube 5.The tubes 4 and l5 are held in fixed position relative to one anotherupon the rod I4 by the non-conducting spacing member 38.

The rod I4 `is provided with a longitudinal groove 32 into which theleaf springs 34 are forced beneath the inside of the tubes 4, and 33withthe sleeves 4 and 5 mounted comparatively loosely on insulator rodI4 and spaced by insulating member 30, these three tubular members areheld slightly eccentric to shaft I4 by the action of springs 34. Despitethe fact that the clearance between moving and stationary capacitiveelements is very small, the requirement of high precision necessitatesthe use of some means toensure stable positioning of the active sleeves.This means must act independently of forces which might be applied tothe over-all condenser structure, as well as those which might beoccasioned by very small shifts of alignment in the internal structureof the condenser, particularly during adjustment. With the assembly ofrod I4, bushing I8 and outer sleeve 8 being secured by pin 22, theopposite end of rod I4 is free to float radially as a cantilever beam.This floating action, taken together with the actions of springs 34,provides a spring-loaded locating force which is constant in directionand magnitude, tending to cause sleeves 4 and 5 to contact thecylindrical inner surfaces of sleeves 8 and 'I along an element line andwith a pressure which does not vary with setting and resetting of thecondenser or with the application of external forces. Thus, undesirablevariation of positioning is restricted to a very much smaller range thancould be achieved by allowing the sliding elements to move within theirclearance in a random fashion. The clearance between rod I4 and sleeves4, 5 and 30 is made greater than the clearance between sleeves 4 and 8or 5 and 1. This is done in order to en sure free action of springs 34in locating sleeves 4, 5 and 30 relative to the internal surfaces ofsleeves 8 and 1.

A control knob 38 is rotatably carried upon the end of the casing 8.This knob consists of two separate portions 38 and 40 which surround awasher 42 that is fixed within the casing 8 with the outer edge of thewasher 42 flush with the end of the casing 8. The two sections 38 and 48of the knob 38 are urged toward one another and are pressed upon thesides of washer 42 by means oi' the screw 44, threaded into a unit 40. Acoil spring 48 serves to press out screw 44 and keep knob 38 frombinding when the screw is not fully tightened. The unit 40 is providedwith a reduced neck portion having slots 48 therein into whichprotrusions 58 from the knob 38 extend and serve to form keys for keyingthe knob 38 to the unit 43. By tightening screw 44 to the limit, knob 38is locked tight against thrust collar 42 and prevents further adjustmentof the unit. 'I'his locking action can be relieved by loosening screw44. When the screw is backed out of the unit 43, the pressure of theinside surfaces of the knob 38 and unit 40 against the washer 42 isreduced so that the force required to rotate the knob 38 is decreasedand the condenser is easily readjusted to any desired position betweenits maximum and minimum capacities.

A tubular sleeve 52 is press-fltted at the end 54 over the recessedportion 58 of the knob section 40. Thus, rotation of the knob produces acorresponding rotation in the sleeve 52. The opposite end and enlargedend 58 of the sleeve 52 is provided with inside threads 80.

The oscillatory member II is slidably carried upon the inner surface ofthe casing 8. Springs 8l and 82 are fitted into and retained in grooves83 and 8,4 and operate to take up play between member I3 and casing 8,causing member i') to move constantly against the same side of casing 8during adjustment of the condenser. This ensures a constantlyreproducible positioning action between casing 8 and member I3 despitethe existence of clearance between these sleeves which may vary withmachining tolerances. Springs II and 82 are so located that their actionin taking up play between casing 8 and member I3 does not create anyforce in opposition to the above-describedactionsof springs 34, i. e.,so that the resultant force of springs 8i and 82 is perpendicular to theforce of springs 34.

The member I3 has an outside threaded end section 85 which intermesheswith the inside threads of the sleeve 52. The movable sleeves 8 and 1are fitted within this oscillatory tube I3 kand are fastened to the tubeby solder connections 88 and 88, thus electrically connecting the metalsleeves 8 and I to the member I3. This soldering is accomplished byscraping off the oxide coating from the sleeves 8 and 1 at the requiredplace and dropping solder upon the scraped portion through matched holesin the member I3.

The casing 3 is provided with a longitudinal slot 18 and a small screw12, which is threaded into the member I3, extends into this slot 10.This screw 12 is of such size that it may slide within the slot.Consequently, the screw 12 permits the member I3 to reciprocate withinthe casing 8, but does not allow the member I3 to rotate within thecasing. Thus, it will be seen that rotation of the knob 38 by suitabletorque causes the sleeve 52 to correspondingly rotate. and because ofthe intermeshing threaded areas 88 and 84. rotation of the sleeve 52forces the member I3, which cannot rotate, toward or away from the knob88. Since the metal sleeves 8 and 'I are fixed within the member I3, thesleeves 8 and 1 are caused to move in or out upon the stationary metalsleeves 4 and 5. Hence, rotation of the knob 38 causes a variabledisplacement between the stationary capacitive elements 4 and and thevariable capacitive elements 6 and 'l of the condenser.

The portion of the casing 8 adjacent to the slot 'l0 is preferablyprovided with indicator markings and in cooperation with a recess 14, orsome similar marking, in the screw 12, the setting of the condenser canbe indicated.

The bottom side of the casing 8 is provided with a longitudinal slot 16through which the electrical connections to the stationary and variableplates of the condenser extend. Thus, an electrical conductor 18 extendsthrough the slot 'I6 and through a hole 80 in the tube 30 into thegroove 32 and is soldered to the inner surface of the sleeve 5 at apoint where the oxide coating of sleeve has been scraped away.Similarly, a second electrical conductor 82 extends through slot 16through a hole 84I in the bushing I8 into the groove 32 and is solderedto the inside of the tube 4. The ground connection 86 to the condenserextends through the slot 'I6 and is fastened to the'oscillatory memberI3.

The drawings show a casing containing two separate condensers providedwith a common Iground connection. However it will Ibe realized thatunits comprising only one or more than two Separate condensers in thecasing may be prepared in accordance with this invention, and that wheretwo or more separate condensers are made in a separate unit, they may beprovided with totally independent leads.

Because the condenserwstructures described above make use of thefree-iioating, springloaded support means in ensuring stable andaccurate radial positioning of the dielectric coated sleeves, theyprovide new degrees of mechanical and electrical stability in variablecondensers. This makes possible the fabrication of an exceedinglyaccurate and stable miniature variable condenser without introducing thepractical restriction of excessively ilne tolerances in the supportingelements. The spring-loading technique employed in this device makespossible for the rst time a highly accurate and reproducible miniaturevariable condenser whose mechanical components need not be held toexceedingly close tolerances in production. As has been pointed out,wide clearances are purposely introduced to allow free action of thespring-loading means.

We claim:

l. A variable condenser comprising a tube, a rod cantilevered axiallyWithin said tube, a stationary metal sleeve embracing said xed rod, adielectric coating upon the outside of said metal sleeve, a movablemetal sleeve having a dielectric coating upon its inner surface, themovable metal sleeve telescoping upon the stationary metal sleeve with aportion of said dielectric coatings slidably engaging one another,separate electrical conductors connected to each of said metal sleeves,and means carried by said tube for moving said movable sleeve lengthwiseto the stationary sleeve.

2. A variable condenser as claimed in claim l, wherein Said rod isprovided with a longitudinal groove which has a spring member insertedtherein beneath the inside of said stationary metal sleeve.

3. A variable condenser as claimed in claim 1, wherein said sleevemoving means comprises a tubular oscillatory member surrounding themovable sleeve, the said tubular member being slidably carried upon theinner surface of the casing.

4. A variable condenser as claimed in claim wherein said tubularoscillatory member com '15 tween the inside of the casing and theoutside prises an outside threaded end portion which intermeshes with aninside threaded sleeve rotatably carried within the casing, said tubularmember being provided with means which prevents said member iromrotating within said casing. and said sleeve being provided with meanswhich prevents it from moving longitudinally in the casing.

5. A variable condenser comprising an elongated hollow casing, astationary metal sleeve fixed axially within the casing, a dielectriccoating upon the outside of said stationary sleeve, a movable metalsleeve having a dielectric coating upon its inner surface, the movablemetal sleeve telescoping upon the stationary sleeve with a portion oisaid dielectric coatings slidably engaging one another, a tubularoscillatory member carried upon the inner'surface of said casingsurrounding said movable metal sleeve having an outside threaded endportion, an inside threaded sleeve rotatably carried within the casingwhich inter-meshes with said outside threaded end portion, said insidethreaded sleeve being fastened at the end opposite to its insidethreaded portion `to a knob which is carried upon the casing for axialrotation with the casing while being held against longitudinal movementrelative to the casing.

6. A variable condenser as claimed in claim 5 wherein said knob isformed of two separate sections which have their opposite faces engagingthe sides of a washer which is fastened flush with the end of thecasing, said knob sections being urged toward one another against thewasher facings by means of a screw.

7. A variable condenser comprising an elongated hollow casing, astationary metal sleeve iixed axially within the casing, a dielectriccoating upon the outside of said stationary sleeve, a movable metalsleeve having a dielectric coating upon its inner surface, the movablemetal sleeve telescoping upon the stationary sleeve with a portion ofsaid dielectric coatings slidably engaging one another, a tubular,oscillatory member carried upon the inner surface of said casingsurrounding said movable metal sleeve having an outside threaded portionthereon, a threaded member carried by said casing that inter-meshes withsaid outsidethreaded portion, movement of said threaded member causinglongitudinal movement in said oscillatory member, whereby an adjustmentof said movable sleeve relative to said stationary sleeve is obtained,and electrical conductors electrically connected to said metal sleeves.

8. A variable condenser as claimed in claim 7, wherein the electricalconductor connected to the stationary metal sleeve extends through anopening in said casing-and is soldered to the inside of said stationarymetal sleeve.

9. A variable condenser as claimed in claim 'l having spring loadingmeans which operate in all three dimensions along lines essentiallymutually perpendicular whereby all undesirable mechanical loosenessbetween separate elements of the condenser is eliminated.

l0. A variable condenser as claimed in claim 7, wherein said stationarymetal sleeve surrounds a non-conducting rod which is positioned axiallywithin said casing.

1l. A variable condenser as claimed in claim 10, wherein said rod isfastened to the casing at one end, said rod being centered within thecasing by means of a bushing which iills the space be- 7 of the rodwhile the opposite end of said rod is free.

12. Avariable condenser as claimed in claim 11, wherein there is aplurality of said stationary sleeves, each stationary sleeve beingcarried by said axially positioned rod, said stationary sleeves beingspaced one from the other by means of nonconducting tubular membershaving the same radii as said stationary sleeves. y

13. A variable condenser comprising a tubular casing, a rod cantileveredaxially within the casing, a stationary metal sleeve embracing saidfixed rod, a dielectric coating upon the outside of said metal sleeve, amovable metal sleeve having a dielectric coating upon its inner surface,the movable metal sleeve telescoping upon the stationary metal sleevewith a portion of said dielectric coatings slidably engaging oneanother, separate electrical conductors connected to each of said metalsleeves, an operating knob rotatably carried axially in one end of saidcasing, said knob being retained against movement longitudinally withsaid casing, a threaded sleeve fastened to said knob, and an oscillatorymember comprising a threaded tubular section intermeshing with saidsleeve threads and means for preventing said member from rotating withinsaid casing, said movable metal sleeve being connected to saidoscillatory member for movement with the member.

14. A variable condenser comprising a cylindrical casing, a rod ofdielectric material positioned axially within the casing by a bushingfixed in one end of the casing around one end of the rod, a longitudinalgroove in said rod, a stationary nickel tube having an oxidized surfaceembracing said rod, a spring member forced into said groove beneath saidmetal tube, a movable nickel tube having an oxidized surface telescopingupon said stationary nickel tube with a portion of the outside oxidesurface of the stationary tube slidably engaging a portion of the insideoxide surface of the movable tube, a washer fastened in the end of saidcasing opposite said bushing, an operating knob comprising two separablesections urged toward one another by a screw, said washer beingpositioned between said sections whereby said knob is rotatably carriedin said casing and held against movement longitudinal with the casing, atubular sleeve fixed by one end to the inner section of said knob havingan inside threaded portion on the opposite end, an oscillatory membercomprising a tube sliding on the inside of said casing having an outsidethreaded portion on one end which intermeshes with said inside threadedportion of said sleeve, and a retaining element extending outwardly fromthe oscillatory member slidably carried in a longitudinal slot in saidcasing preventing rotation of said oscillatory member within the casing,said oscillatory member being connected to said movable nickel tubewhereby longitudinal movement of the oscillatory member within thecasing causes a corresponding movement in said movable tube, andseparate electrical conductors electrically connected to each of saidnickel tubes.

15. A variable electrical condenser comprising a tubular casina, a shaftof dielectric material positioned axially within the casing andcantilevered in a bushing fixed in one end of the casing, a stationarytubular capacitive element having a dielectric surface coating`supported upon said shaft, a spring member positioned between saidshaft and element holding an inside portion of the element always inengagement with an outside portion of said shaft, a movable tubularcapacitive element having a dielectric surface coating telescoping uponsaid stationary element with a portion of the outside surface of thestationary element slidably engaging a portion of the inside surface ofthe movable element, an oscillatory tubular member slidably carriedwithin said casing, spring members between said casing and saidoscillatory member so positioned that the resultant force of saidlast-mentioned spring members is perpendicular to the force of saidfirst-mentioned spring member, said movable element being carried bysaid oscillatory member for movement with said member, means forpreventing said oscillatory member from rotating within said casing andmeans for oscillating said oscillatory. member longitudinally withinsaid casing.

ROBERT P. GUT'IERMAN. ALEX J. BIELSKI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Clark Oct. l2, 1948

